Maintenance-friendly immobilization system

ABSTRACT

A motor vehicle immobilization system having an anti-theft control device (13) and a function control device (10, 11) which is released by a regular unlocking communication with the anti-theft control device (13). To permit simple maintenance of individual engine function units, the function control device (10, 11) has bypass means (204 through 220) which permit an atypical unlocking of the function control device (10, 11) by the external device (19). The bypass means (204 through 220) include a time-delay device (206, 218) which, during atypical unlocking, only releases the function control device (10, 11) after the passage of a predetermined delay time (T F ).

STATE OF THE ART

The invention relates to a vehicle immobilization system for a motorvehicle, having an anti-theft control device for performing auser-legitimization check and having at least one function controldevice for controlling the operation of an engine component, with thefunction control device being connected to the anti-theft control deviceby a line or conductor system. Devices of this type are being used moreand more frequently to combat the increasing incidence of auto theft.Their mode of operation is based on only enabling the function ofcontrol devices necessary for vehicle operation, for instance a devicefor operating the diesel shut-off valve or motor control device, if acode entered by the user matches a code stored in advance in the controldevice. A special operating situation arises if the control devicecontrolling the motor function unit is intended to be operatedseparately from the vehicle. This is typically the case during enginemaintenance, for example when the diesel pump and consequently thedevice that controls the diesel shut-off valve are to be tested on atesting bench. The function unit must then be able to be enabledexternally, that is, without involvement of the legitimization testingdevice present in the vehicle for this purpose. This can be-effected ina simple manner by manually supplying the code, with suitable inputmeans, which would otherwise be supplied by an anti-theft controldevice. In this instance, the correct code must be known to the personperforming the test. This is, however, a disadvantage both with respectto maintenance friendliness and with respect to the security effect.Namely, the owner of the vehicle must know the code. Frequently,however, the code is transferred to the vehicle without ownerinvolvement, for example in the form of transponder triggering. Usuallythe owner does not know the correct code. It must therefore typically beregistered externally, for example, on a card. However, in this case thedanger of the user misplacing the card automatically increases. On theother hand, the option of enabling a function unit by externallysupplying the correct code, bypassing the anti-theft control device,facilitates startup of the vehicle by an unauthorized user. Essentially,only external unlocking means are required for manual enabling, such asthose also used for authorized maintenance in a workshop. If a thiefhaving this type of equipment additionally obtains the code, he can puta vehicle into operation without difficulty.

The object of the present invention, therefore, is to configure ananti-theft device for motor vehicles such that it permits simplemaintenance of the motor function unit incorporated into the protectiondevice without limiting the security effect.

SUMMARY OF THE INVENTION

The above object generally is accomplished according to the presentinvention by a vehicle immobilization system for a motor vehicle, havingan anti-theft control device for performing a user-legitimization checkand having at least one function control device for controlling theoperation of an engine component, with the function control device beingconnected to the anti-theft control device by a conductor or linesystem, and wherein the function control device includes a circuit whichprocesses digital signals and only permits startup of the functioncontrol device after a regular unlocking communication with theanti-theft control device has taken place, and further includes bypassmeans which permit an atypical unlocking of the function control devicein response to a communication from a device which is external to thevehicle if the regular unlocking communication is omitted, whichexternal device acts directly on the function control device, bypassingthe anti-theft control device. The unlocking of a protected enginecomponent is only possible by means of a special, atypical unlockingprocedure. In particular, this procedure encompasses steps that requirethe passage of down time. Consequently, it is not possible forunauthorized uses to start a vehicle in a short time withoutlegitimization, even if they have access to the necessary release means.The time-intensive release procedure does not disturb maintenance jobs.It can be performed automatically for the most part, so that thenecessary down time can be used for other purposes.

It is very useful to equip the protected engine components with atime-delay that only allows the associated engine components to be putinto operation after the passage of a predetermined delay time at thebeginning of the atypical unlocking procedure.

The device according to the invention can be manufacturedcost-effectively. It is advisably embodied as a software solution in theform of a program inside a logical circuit which is provided anyway fora protected engine component. Therefore, existing arrangements caneasily be retrofitted with the device.

An advantageous increase in anti-theft security ensues in that thesupply of a predetermined signal by way of the release means isperiodically requested during the delay time. The user involved with therelease is thereby required to repeatedly turn to the engine componentto be enabled. An unauthorized, secretive starting of the vehicle istherefore practically no longer possible.

The external startup device advisably has suitable input means for inputof the required predetermined signals. For example, these means cancomprise a keyboard. It is also possible, however, to enter the requiredpredetermined signals by way of a switch present on the enginecomponent, for example, the gas pedal.

Moreover, it is advantageous to release the vehicle for a predetermined,small number of startups after the atypical startup procedure has beenperformed. The number is particularly based on the average requirementswithin the scope of maintenance.

An embodiment of the proposed security device is described in detailbelow with reference to the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a block diagram of a vehicle immobilization systemaccording to the invention, and FIGS. 2a and 2b are a flow chart of thecourse of an atypical unlocking procedure.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a typical design of an anti-theft device, hereinafterreferred to as vehicle immobilization system, as it forms the basis ofthe present invention. The crux of the illustrated arrangement is ananti-theft control device 13, hereinafter referred to as immobilizer.One or a plurality of function control devices 10, 11 is or areconnected to the immobilizer 13 by way of a line system 12. In theexample, this is a device 10 for operating the shut-off valve at thediesel pump. All of the function control devices 10, 11 respectivelymake use of their own microprocessor or a similar circuit that processesdigital signals. In connection with a control program, the circuitverifies the control functions performed by the function control device.Furthermore, the immobilizer 13 uses a receiving device 14 for supplyinga vehicle/user-specific code for a legitimization check. As shown inFIG. 1, this code can be supplied by a transmitting device 16 which canin turn be disposed in the vehicle key, for example. This supply isfrequently effected without contact, for example by an infrared orhigh-frequency signal. It can, however, also be effected by way of akeyboard connected to the immobilizer 13 by way of a line. A pluralityof further variations known in the technical field also exists forimplementing the supply of the code to the immobilizer 13.

The arrangement illustrated in FIG. 1 operates as follows. To start thevehicle, first the user transmits the user/vehicle-specific code to theimmobilizer 13. The immobilizer 13 compares the received code to a codestored in a memory. If the received code and the reference code match,the immobilizer 13 unlocks the function control devices 10, 11. To thisend it effects a regular unlocking communication with the functioncontrol devices 10, 11. This communication advisably includes a furthercomparison of the codes, with a code generated by the immobilizer beingcompared to a code present in the function control device 10, 11. Theunlocking communication ensures that the used immobilizer 13 isregularly a part of the function control devices 10, 11. If the check ofthe user code or the unlocking communication takes place in apredetermined manner, and in articular if the checked codes respectivelymatch the present reference codes, vehicle operation is enabled.Otherwise, the function control devices 10, 11 remain blocked, so thatvehicle operation is not possible.

In accordance with the invention, enabling of a function control device10, 11 is also possible if the device was separated from the immobilizer13 or line system 12. This is the case, for example, if a functioncontrol device 10, 11 is to be tested in the removed state by means ofan external device 19. External device 19 is typically a diagnosticdevice, as indicated in FIG. 1. It can be connected to the functioncontrol devices 10, 11 by way of an interface 18, 18'. For enabling, inthis case the function control devices 10, 11 also make use of bypassmeans which permit enabling of the function control devices 10, 11 inconnection with an atypical unlocking procedure. These means areadvisably embodied in the form of a program within the control programsof the function control devices 10, 11.

FIG. 2 shows the course of an atypical unlocking procedure. It startswhen the function control device 10, 11 checks whether a regularunlocking procedure is performed, step 200. This check is a component ofthe regular unlocking procedure, and is effected with each unlocking. Ifthe result of the check is positive, the one regular unlocking procedureis performed. The above-described unlocking communication follows. Ifthe result of the check in step 200 is negative, the function controldevice 10, 11 checks in step 202 whether the unlocking should beperformed in an atypical manner by an external device 19 which is notnormally a part of the vehicle, and whose identification is stored in amemory in the function control device 10, 11. An example, of this typeof device is a diagnostic device 19. If an attempt is made to performthe unlocking with a device that is unknown to the function controlunit, the identification of which device is not stored in the memory,the unlocking procedure is halted and the function control device 10, 11remains locked, step 203. It is not possible to start the vehicle.

If, in contrast, the external device 19 used for unlocking possesses anidentification that is known to the function control device 10, 11, theatypical release procedure is initiated in step 204. In step 206 a firstcounter is started which detects the passage of a release time T_(F). Itdetermines the amount of time by which the actual operation release ofthe function control device 10, 11 is delayed with respect to thebeginning of the atypical release procedure. Its value lies in a rangeof a few minutes, for example 15 to 50 minutes.

In step 208 the function control device 10, 11 transmits a block ofcontrol data to the external device 19 used in unlocking. It serves onthe one hand to verify the connection line between external device 19and function control device 10, 11, and on the other hand to ensure thatthe external device 19 is authorized for the atypical unlocking. In step210 the function control device 10, 11 verifies whether the externaldevice 19 has responded in a predetermined way within a predeterminedtime dt. If the result of this check is negative, the atypical unlockingis halted, step 203, and the function control device is locked.

If the result of the check in step 210 is positive, a check is made instep 212 to determine whether the counter time Tr is greater than apredetermined time window t₁. The time window determines at which timesa user is requested to make an entry within the framework of an atypicalunlocking procedure. It is dimensioned, for example, according to therelationship t₁ /T_(F) =3, so that three additional entries arenecessary within the release time T_(F). If the time window t1 has notpassed, in step 218 the function control device checks whether therelease time T_(F) has passed. If this is likewise not the case, steps208 through 218 are repeated.

If the check in step 212 reveals that the time window t1 has passed, itis first reset to the value 0 in step 213. The course of the time windowT_(F) is then interrupted. The function control device 10, 11 now waitsfor the external device 19 to make an entry. The entry can be made, forexample, by pressing a key or entering a code, e.g. by means of an inputdevice 20 such as a keyboard. Alternatively, the requested entry may beprovided by an input device 21 already provided on the engine componentbeing controlled, for example, the gas pedal or a switch. In step 217 acheck is made to determine whether the entry has been made. If this isthe case, the time window T_(F) is restarted, step 219; step 218 issubsequently performed.

If the check in step 217 reveals that no entry was made, or that theentry does not possess a predetermined form, the atypical releaseprocedure is again halted, step 219; the function control device 10, 11remains locked.

If the query in step 218 reveals that the release time TF has passed,the function control device 10, 11 is released. Following the release ofthe function control device 10, 11, a test communication with theexternal device 19 further takes place cyclically. Analogously to step208, in step 222 a control block is sent to the device 19. Subsequently,in step 224 a check is made to determine whether a predeterminedresponse has been given within a predetermined time dt and thecommunication is therefore in order. In step 225 a check is made todetermine whether a signal indicating the end of operation is present.If this is the case, or the check in step 224 reveals a communicationerror, the function control device 10, 11 halts its operation and locks.If a signal for the end of operation is not present, and thecommunication is in order, steps 222 through 225 are repeated. Aplurality of modifications are possible which retain the conceptunderlying the device of the invention. The sequence of the processsteps illustrated in the flow chart according to FIGS. 2a and 2b cantherefore be interchanged, or the steps can even be omitted completely.The latter applies, for example, to the additional entry required bysteps 211 through 217. Process steps 208 and 210 or 222 and 224 forchecking the line connection between external device 19 and functioncontrol device 10, 11 can be omitted or embodied in a completelydifferent manner.

The release can be effected for a one-time startup, but also for apredetermined, small number of releases. The latter solution is mostuseful if a function control device 10, 11 must regularly be startedseveral times during maintenance.

We claim:
 1. In a vehicle immobilization system for a motor vehicle,having an anti-theft control device for performing a user-legitimizationcheck and having at least one function control device for controllingthe operation of an engine component, the function control device beingconnected to the anti-theft control device by a line system, theimprovement wherein the function control deviceincludes a circuit whichprocesses digital signals and only permits startup of the functioncontrol device after a regular unlocking communication with theantitheft control device has taken place, and further includes bypassmeans (204 through 220) which permit an atypical unlocking of thefunction control device by a device which is external to the vehicle ifthe regular unlocking communication is omitted, which external deviceacts directly on the function control device, bypassing the anti-theftcontrol device.
 2. Vehicle immobilization system according to claim 1,wherein the bypass means, in an atypical unlocking, first releases thefunction control device after the passage of a predetermined delay time(TF) at the beginning of the atypical unlocking.
 3. Vehicleimmobilization system according to claim 2 wherein, during the delaytime (T_(F)), the bypass means periodically request the external devicethat a predetermined signal be supplied.
 4. Vehicle immobilizationsystem according to claim 3, wherein the external device has input meanswith.which the predetermined signal is to be entered and supplied. 5.Vehicle immobilization system according to claim 3, wherein thepredetermined signal is supplied by input means already present in thecontrol device.
 6. Vehicle immobilization system according to claim 1,wherein the function control device is unlocked for a predeterminednumber of unlocking procedures during atypical unlocking.